With the ever increasing demand for more function designed into smaller spaces, process geometries have gotten dramatically smaller. This progress in technology has enabled the development of highly popular electronic devices, such as cell phones, hand held computers, personal GPS navigation systems, and personal music video players. Our social reliance on these innovations has put very stringent reliability requirements on the products that we select.
As device dimensions have continued to shrink, the packing density of the semiconductor devices, e.g. transistors, has increased. That is, ever increasing numbers of transistors or memory cells are located on the same plot space of a semiconductor substrate. As a result of this increased device density, the conductive metal lines and contacts or vias that connect these various devices have also been reduced in physical size, and they are also packed more closely together. In general, the resistance of a metal line is inversely proportional to the cross-sectional area of the metal line. Thus, all other things being equal, it is important that the cross-sectional area of the metal line be maintained above certain minimum levels such that the resistance of the metal line does not exceed allowable limits. Unanticipated increases in the resistance of a metal line may adversely impact device performance, e.g., a reduction in operating frequency, increased heat build-up, increased power consumption, etc.
Unfortunately, a phenomenon known as electromigration can adversely impact conductive metal lines in an integrated circuit product. In general, electromigration is a process whereby a conductive structure, such as a metal line, contact or via tends to degrade or become damaged, thereby resulting in a change in the physical characteristics, e.g., shape, size, etc., of the conductive structure. Typically, electromigration occurs when a current is passed through relatively long conductive structures. The current sets up an electrical field in the conductive structure that decreases from the input side to the output side of the conductive structure. The electric field thereby biases the movement of the metal atoms in the conductive structure. This electromigration phenomenon results in physical changes to the size and/or shape of the conductive structure. For example, in some cases, a void may form in the conductive structure. In a worst case scenario, electromigration can cause complete separation of the conductive structure. This electromigration phenomenon can occur on metals such as aluminum, copper, tungsten, titanium, etc.
In designing integrated circuit products, efforts are taken to reduce, eliminate or account for electromigration of conductive structures in integrated circuit products. Such efforts may include selecting appropriate materials, making conductive structures sufficiently large such that the effects of electromigration does not adversely impact the performance of the integrated circuit product over its useful life. To verify the integrity of current designs, devices are tested for thousands of hours under stress conditions, such as elevated temperature, voltage and humidity. The late discovery of a flawed design can be devastating to a product delivery schedule.
Thus, a need still remains for a system that will allow integrated circuit designers to predict the impact of electromigration on their design prior to manufacture. The demand for highly reliable and long life products make it is increasingly critical that answers be found to these problems. In view of the ever-increasing need to save costs and improve efficiencies, it is more and more critical that answers be found to these problems. Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.